Propellant powders



Patented Apr. 23, 1929.

UNITED STATES PATENT OFFICE.

ARTHUR ONEIL, OF ALTON, ILLINOIS, ASSIGNOR T WESTERN CARTRIDGE COM- PANY, OF EAST ALTON, ILLINOIS, A CORPORATION OF DELAWARE.

PROPELLANT POWDER-S.

N0 Drawing.

This invention relates to progressive powders and more particularly to progressive burning propellant powders adapted for use in small arms such as shot guns.

The term progressive burning is usually applied to propellant powders used in small arms and is associated with those powders which have received a surface treatment. This treatment being either a superficial coating or an impregnation of the surface layers of the powder grain by a solid which is a solvent for the powder and usually at an elevated temperature. This serves to. delay -the=rate of. ignition and its propagation from one grain of powder to the other, thus reducing the unit pressure within the gun barrel. It will, however, be noted that a coated powder having the same base compo. sition, will require a larger charge to produce equal velocity with an uncoated powder.

Slow burning powders, especially those having a nitro-hydrocarbon base and progressive burning, are not adapted for use in shot guns, unless the loaded shot shell is especially designed as described in application Serial Number 667,075,.filed October 6, 1923. A dense nitro-cellulose colloid burns progressively, that is, in layers until completely consumed. While it is, therefore, peculiarly adapted for rifle arms where the projectile seals the bore. it is not suitable for'cylinder guns and small arms. In powders for cylinder guns, it is necessary that the initial burning be at a more rapid rate, due to the fact that the bore of the gun is not sealed by the projectile. Accordingly if the pressure is not rapidly developed, incomplete burning results, since the rapidity of burning depends directly upon pressure. Accordingly where a dense nitro-cellulose powder.is employed in a cylinder gun, the result-will be u'nburnt powder and escape of the gases around the wads, thereby reducing the ballastic efficiency.

In the preparation of nitro-cellulose powder for use as military ammunition, it has further'been the practice to subject the dense nitro-cellulose colloid to surface treatment by coating or impregnating the same with a suitable nitro-hydrocarbon, thereby producing a so-called progressive burning powder having a still lower initial pressure without, however, lowering the velocity of the pro- Application file d June 20, 1924. Serial No. 721,203.

j ectile. The function of the solvent, however,

is to act as a deterrent, as this solvent is not In order to produce a smokeless powder having a nitrocellulose base, it has been the practice heretofore to either mix with the nitro-cellulose, metallic nitrates or amore violent explosive ingredient, such as nitroglycerin. The former, however, produces "smoke, while both have a corrosive action on the bore of the gun. It has also been the practice to employ weak solvents so as to only partially gelatinize the nitro-cellulose, or to employ ingredients with the nitro-cellulose while in a plastic state which are subsequently extracted. These, however, are open to the objection that they do irot provide sta ble and uniformly burning grains.

It is a well known fact that powders of various grain, size and shape, have Various, rates of burning and produce var'ous pressures and temperatures when fire in a gun barrel, e. g. a certain weight of very finely divided nitro-cellulose powder will burn very rapidly and 'producq. high pressures while heavier grains will burn more slowly under given conditions, the largest .grains will not produce sufiicient pressure and temperature to completely burn the grain.

The rate of burning of a powder grain is also dependent upon the density and composition. Thus a nitro-cellulose powder grain of comparatively low density, such as the bulked smokeless powder described in my Patent No. 1,627 ,861, issued May 10, 1927 or even ordinary bulk smokeless powder, has a higher rate of burning than, for instance,

condensed colloided nitro-cellulose' powder. Also the latter in turn has a lower rate of burning than, for instance, a low nitration nitro-cellulose' bulk powder or a nitro-glyc erin-nitro-cellulose powder. In, all of the above powders the grain'characteristics de termine the rate of burning.

One of the objects of this invention, there-' fore, is to provide a progressive burning that the grains of the several portions burn at While the grain characteristics of the same charge.

progressively decreasing rates and the portions so chosen are then blended in the desired proportions so as to produce the desired progressive burning of a blended charge.

portion may be substantially the same, the grain characteristics of the several portions vary progressively in accordance with the desired progressive action of a blended In accordance with one embodiment of this invention the rate of burning is controlled by proper selection of the grain sizes. By proper selection of the grain sizes in the several portions, i. e., by selecting powder portions in which the sizes of the grains increase progressively in the several portions, then a blended charge will burn progressively. As an example, a powder for use in shot guns may consist'of ground or cut dense colloided nitro-cellulose powder, either surface treated or untreated, and blended in the following proportions 10% thru a 40 mesh screen on 42. 20% thru a 42 mesh screen.

20% on a 46 mesh screen. 50% thru a 46 on 60. L

This powder in a trap load (shot shell) gives 882 foot seconds with a pressure of 5 5130 pounds per square inch as compared with the standard load (bulk smokeless) of 860 foot seconds with 8500 pounds per square inch.

In such a charge the finer or quick burning grains will ignite at a lower pressure and temperature than the coarser or slower burning grains; the temperature and pressure will, however, be maintained and even elevated by the combustion of the finer grains, to an extent sufficient to cause and maintain the combustion-of the larger grains. Thus in the firing of a blended charge in which 'the grain sizes increase progressively, the

primer need only be sufficient to start ignition of the finer grains; these will'maintain the temperature and pressure necessary to ignite the next coarser grains; and so on. In this manner is produced a delayed ignition of the charge as a whole and a true progressive burning; accordingly for a blended charge the velocity is greater although the maximum pressure is less than for a standard charge as will be seen from the results given above.

In accordance with another embodiment of this invention the rate of burning is controlled by proper selection of the grain density. Thus by proper selection of, for instance, a portion of dense colloided nitrocellulose powder and a portion of bulk smokeless powder, or a bulked nitro-cellulose powder, such, for instance, as described in my Patent No. 1,627,861, the desired progressive burning action may be'obtained. The following is also an example of a rifle powder in which the grains may be of uniform size and the base nitro-cellulose. high nitration powder-coated with9% dinitrotoluene.

10% low nitration powdercoated with 5% dinitrotoluene.

10% low nitration powderuncoatcd.

The above blended mixture produces Veloc- 'ities equal with the first 80% component of the-mixture above, but with a smaller charge.

In accordance with still another embodiment of this invention the rate of burning is controlled by proper'selection of the grain composition. Thus a powder adapted for use in shot gun shells containingheavy shot, such as buck shot, is as follows:

80% dense colloided intro-cellulose powder of high nitration and coated with dinitrotoluene.

20% nitro-cellulose-nitro-glycerin powder of low nitration and uncoated.

Such a powder has given satisfactory re sults in high velocity buckshot loads.

An example of controlling the rate of burning by varying both the grain sizes and composition is as follows: I

90 %80% ground smokeless powder dense colloidcd nitrocellulose, either coated with'dinitrotolucne or uncoatcll) sized as follows:

66%% through 40 mesh on 46. 33 A; through 46 mesh on 70. 10%-20% black powdc1'3 F G.

Another example of mixed grain, size and composition is as follows:

90%8l0% ground smokelesssame as the preceding exam 0. 10%-20% powder consisting. of, 70% potassium nitrate. 15% barium nitrate.

15% charcoal.

' a The charcoal (or cellulose) may be impregnated with the potassium nitrate (or sodium nitrate) andthe barium nitrate by a soaking and drying process. K The above powder in a standard shot shell load gives 1037 foot secohds with7346 per square inch as against 985,

foot seconds with equal pressure when using standard load of bulk smokeless powder.

In accordance with thisv invention there fore, the progressive burning action is produced by proper selection of the grain characteristics of the portions of the blended charge; and by the proper selection of'the proportions of the charge portions the desired progressive burning can be obtained. This grain characteristic may be varied by variationof the size, shape, density or composition of the grain, and the selection may be of any of these characteristics or of any combination of them. In accordance with this invention the more rapid burning powders impart their energy directly to the slower burn- 1 readily ignitable powders will keep up the pressures and temperatures necessary to secure the desired progressive burning ofthe blended charge, while the heavy wadding serves to confine the blended charge. Accordingly the rate of combustion will increase so that the desired pressure is maintained, especially since the heavy wadding provides suflicient resistance to the expansion of the gases to maintain the pressure. The result 'is, therefore, that the combustion is uniformly accelerated, even after the confining wadding and the shot begin to-move, so that the pressure is maintained nearly uniform for an extended distance along the gun barrel; the result is that the shot charge is uniformly accelerated under a lower initial pressure maintained for an extended distance along the gun barrel.

While in the specification and claims the term grain is used, it is to be understood that it is intended as a word of general description and not of limitation, but to include the various forms in which powder is produced for use. It will be further understood that while theories of formation and operation have been advanced, the invention is not necessarily limited thereto. It will further be obvious that various changes may be made in details without departing from the spirit of this invention; it is, therefore, to be understood that this invention is not to be limited to the specific details described. Certain features disclosed in this application are claimed in applications Serial Nos. 62,090 and 62,091, filed October 12, 1925.

Having thus described the invention, what is claimed is:

1. A progressive burning powder consisting of blended grains, the characteristics of which are so chosen as to cause a. blended charge thereof to burn progressively.

2. -A progressive burning powder consisting of blended portions, each portion having acharacteristic which is different from that of the other, the characteristics of the grains of the several portions being so chosen as to cause a blended charge thereof to burn progressively.

3. A progressive burning powder consisting of blended portions, the characteristics of the grains of each portion being substantially the same but the characteristics of the grains of the several portions being so chosen as to cause a blended charge thereof to burn progressively.

4. A progressive burning powder consisting of blended portions, the grains of the same portion burning at substantially the same rate but the grains of the several portions burning at different rates.

5. A progressive burning powder consisting of blended portions, each portion having agrain size which is different from that of the other, the sizes of the grains of the several portions being so proportioned. as to cause a blended charge thereof to burn progressively.

6. A progressive burning powder consist ing of blended portions, each portion having a grain size which is different-from that of the other, the sizes of the grains of the several portions and said portions being so relatively chosen as to cause a blended charge thereof to burn progressively.-

7 A progressive burning powder consisting of blended grains, the sizes of which are so chosen as to cause a blended charge thereof to burn progressively.

8. A progressive burning powder consisting of blended portions, each portion having a grain size which is difierent from that of the other, the grains of each portion being of substantially the same size but the sizes of the grains of the several portions being so chosen as to cause ablended charge thereof to burn progressively.

9. A progressive burning powder consisting of blended portions, each portion having a grain size and density which is different from that of the other, the characteristics of the several portions being so chosen as to cause a blended charge thereof to burn progressively.

10. A progressive burning powder consisting of blended portions, each portion having a grain size, density-and composition which is different from that of the other, the characteristics of the several portions being so chosen as to .cause a blended charge thereof to burn progressively.

' 11. The process of making progressive burning powder consisting in blending powder portions in which each portion has a grain characteristic which is different from that of the other and so choosing the grain,

characteristics of the several portions as to cause a blended charge thereof to burn progressively.

12. The process of making progressive burning powder consisting in blending p'or- 5 portions of these portions as to cause a blended charge thereof to burn progressively.

13. The process of making progressive burning powder consisting in selecting powder portions so that the grains of the 0 several portions burn at progressively 'decreasing rates and blending the portions,

14. The process of making progressive burnlng powder consisting in selecting powder portions so that the grains of the several portions are of progressively increasmg sizes and blendin the portlons.

15. The process 0 maklng progresslve burning powder consisting in selectingpowder portions so that .the grains of the several portions are of progressively increasingsizes and densities and blending the portions.

In testimony whereof I afiix my signature this 5th dayof June, 1924.

ARTHUR s. ONEIL. I 

